Manufacture of sensitized photo



' Reissued Oct. 17, 1 939 UNITED STATES .MANUFACTUREU PATENT-HGFEQE daarmo PRINTING PAPER AND CLOTH John .llolden, Stockport, England, assignor to- Keuffel 85 Esser Company, Hoboken, N. L, a

corporation of New Jersey 1 No'm awmg. Original application No. 2,158,422

datedMay 16, 1959, Serial No. 192,891, Febru- '.ary 26, 1938.

ruary 27, 1937 14 Claims.

- invention has reference to the manufacture of sensitized photographic printing papers and cloths and refers particularly topapers and cloths of the type used for-making, what are called blue prints by the ferroprussiate process, and has for its object to provide-an improved paper in which a better' contrast between the white lines and the blue background is obtained and which paper will also keep without deterioration for long periods. l r

The present invention produces an improved paper or cloth which can be developed or. washed in the usual manner but is also particularly suitable-for producing prints by the so calledfsemiing of blue-prints is made by applying to the dry" process of development in which a. thin film' of liquid is applied as a developer to the surface as distinct .from: the common wet or washing developing operation.

According to this invention a paper or cloth (hereinafter referred to as papeD-Ior the maksurface one or more solutions in neutral or alkaline conditions, containing an iron salt, an ironcyanogen compound which may be-either a ferricyanide, a term-cyanide, or both, buiier salts and a nitrite, in one solution, or the nitrite being applied in asepa'rate solution. 1

The invention can 'be carried out in several ways as hereinafter'exemplified, and the nitrite used is a nitrite of a suitablem etal or base, such as sodium, potassium or ammonium nitrite,-.

which will act as an acid absorbing agent when called upon to do so; that is to say it has a quantitive reaction with acids or acidic salts with which it comes in contact before exposure to' light and consequently will keep thepaper or cloth in the required neutral or alkaline condition.

' Ihe blue print coating solution before ap- I plication to the paper is preferably slightly alkaline or in other words has a pH value ofabove 7, but it'may be neutral as that 'termis under-- stood in this art and used in this specification which covers those solutions with a hydrogen ion concentration of at least one unit- 'asmeasured in pH values-'on either side of the theoretically neutral point of pH' 'E.

all blue print coatings'on the usual. paper bases when washedofl' produce solutions which have hydrogen ion concentrationsmeasured by pH values'that are substantially more acid, i. e..

lower, than the hydrogen ion concentration of theoriginal solutions. The hydrogen ion concentrationof the dry coating on the paper cannot be measured.

Substantially Application for reissue August 1939, Serial -No., 291,949.

In Great Britain Feb- Blue print coatings applied according to the teachings of this specification, whether neutral or alkaline solutions before application, are preserved against deterioration after application.

The nitrite alsowill counteract the acid nature of some of the oxidizing agents which. may be applied to the paper prior to exposureto light to aid intensification and will also counteract the acidity of prints when developed by acidic or' acid-containing developers by the semi-dry process in which a developer is applied to the I exposed print.

In addition to the acid absorbing properties,

:the nitrite when in contact with acids or acidic salts has an oxidizing actioiwhich in some instances may assist in the intensification "'ofthe print.

A chlorate maybe used to provide a mildoxidizing action.

The coated or sensitive surface may be coated with a developing or intensifying 'oxidizing agent in the term of-a fine dry powder; such a powder being e. g. aperoxide of an alkaline earth metal, a hypochlorite, 'a. persulphate, a

chlorine substitution derivative of an aromatic sulphonamide or a chromate.

Examples of working according to the inventlon are as follows: I

Example I A suitable paper is coated in any convenient manner with a solution of the following com-' position:

200 gms. ferric ammonium oxalate.

' 15 gms. borax are dissolved in water and made Example If I A suitable raw paper is coated on one side, with a light sensitive ferroprussiate or blue print solution, according to Example I and dried, the dry sensitive surface is then dusted over in any convenient manner such as by means of a felt pad 400 gms. rice starch powder.

v with adry powder of the following composition: l gms. P. sulphondiehloraminobenzoic acid.

Excess of powder is removed by means offast rotating brushes in light contact with the pow dared surface. The powder adheres in ,and/or on the surface in the form of aflrm layer not easily removed by mechanical friction.

When exposed to light under a design the prints are washed intwater, development takesplace in the usual manner but afterwards the oxidising agent being only slightly soluble commences to act on the light blue background and rapidly proceeds until a .very deep blue is ,obtained, this oxidising or intensifying action being accelerated by heat.

' sa pl In f A suitable paper is coated in any convenient manner with a solution" of the following compositlon:

406 gmsIferric'ammonium oxalate. gins. borax.

The'above are dissolved in water to a volume of 1000 ccs. m which is added:

s 140 gms. potassium ferrocyanide.

30 potassium ferricyanide.' I 125 gms. potassium oxalate (neutral). 250. gms. potassium chlorate. Water to a volume of 3000 ccs.

To the mixed cold solutions there isfadded:

.l00'gms. sodium nitrite. 1

\ 'Apaper so prepared is developed after exposure to light under a design with a solution of the followingcomposition:

l00 gms. zinc-sulphate. e

.100 gms. mono sodium orthophoaphate. gms. magnesium sulphate; 30 gms. ammonium persulphate. Water to a volume of 1000.

cal means such as bycontact with a roller revolYi gin a bath of the solutiomexcess being at the most suitable quantity to may fade under a bright light.

removed by scraper or squeegee rollers.

In, Example 131- it is necessary to apply sufficient developer not o'nly to fix the lines,- and bring up the background, .but 'aiso'to stabilize the, background, as unless this {Care must be taken therefore to use an adequate quantity ofdveloper "and'at first it may be necessary to'makeoneor two tests to arrive make the best and most lasting prints.-

Example IV Asuitablepaper is coated in manner with .a solution of:

50 gms. Soluble starch.

25 gins. sodium nitrite. Y

1 litre of water. I 1

and the paper is then an afterwards coated with the solution in Example I without the nitrite.

The nitrite and the chlorate may be in non-.

- aqueous solutions and maybe applied at any convenient stage. Caremust be taken by the use of buffer salts, mild alkalis or other. suitable means to prevent its, or their premature decomposition. r l

, It has. been found that a; chlorate and a nitrite The solutionis preferably applied mechaniis done the print.

any"convenient "persulphate. a w form mm,"

together are particularly useful in the manufacture of iblue printpapers" which it,is desired to develop without the usual washing operation. The chlorate stabilizes the blue background and the nitrite assists in the formation of clear white lines, andalso helps to keep 'the paper in good condition before use.

What I claim as my invention secure by letters Patent is: '1. Blue print paper suitable for producing and desire prints by the semi-dry development process having on its surface a' non-acid coating comprising a soluble ir6n' salt, an iron-cyanogen compound, a buffer salt and a soluble nitrite.

-2. Blue print paper as defined in claim 1, in

which the soluble iron salt is'a ferric saltand the iron-cyanogen compound is a ferrocyanide.

3. Blue print paper as defined in claim 1', in which the soluble iron salt is a ferrous salt and the iron-cyanogen compound is a fern-cyanide.-

I {4. Blue print as defined. in claim 1, in which the coating comprises both ferroand ferrioyanides. I

. 5. Blue print" paper as defined in claim 1, in

whlchthe coating comprises a soluble chlorate.

and an iron-cyanogen compound together with a soluble nitrite.

.9. A blue print paper having on its surface a blue print coating comprising a soluble iron salt,

an iron-cyanogen compound and a buffer salt together with a soluble nitrite.

10. A blue print paper having on its surface a.

blue print coating comprising a soluble iron salt and an iron-cyanogen compound together withv asoluble nitrite and an oxidizing agent. 11. Ablue print paper having on its surface a blue print-coating comprising a soluble iron salt, an iron-cypnogen compound and an alkali metal oxalate together with an alkali metal nitrite.

12. A method for preparing blue print paper which comprises applying to the paper. a coating "solution containing a soluble iron salt, an ironcyanogen compound, a buffer salt, and a soluble 13. A method for preparing blue prints whic comprises applying to the paper a coating solu-' tion containing a soluble iron salt, an ironcyanogen. compound, a buffer salt and a soluble nitrite, drying the coated paper, exposing the coated paper anddeveloping the print with an oxidizing solution of a zinc salt, and a phosphate.

14. A method for preparing blue prints which comprises applying to the paper a coating solution containing a soluble iron salt, an iron-cy- -anogen compouncL'a buffer salt and a soluble nit ite, drying the coatedpaper, exposing the coated 'pi'iperuand developing the print witha solution of zinc sulphate, mono. sodium ortho-,

phosphate, magnesium sulphate-and ammonium nitrite and drying the coated paper. i 5 

